Means for imparting tension to the drawn-out thread for sewing machines

ABSTRACT

According to the invention, the drawn-out thread of a sewing machine is guided between a roller having a thread releasing notch formed in part of the roller periphery and a thread urging member urged against the roller periphery, with the roller rotated in the direction opposite to the direction of withdrawal of the thread, so that the thread can be effectively rendered taut and loose alternately by the co-operation of the roller and thread urging member.

United States Patent 1191 Matsumoto Jan. 22, 1974 MEANS FOR IMPARTING TENSION TO THE DRAWN-OUT THREAD FOR SEWING MACHINES [75] Inventor: Mitsuo Matsumoto, Tokyo, Japan [73] Assignee: Nara Mishin Kogyo Kabushiki Kaisha, Tokyo, Japan 22 Filed: Dec. 28, 1971 211 App]. No.2 213,080

[30] Foreign Application Priority Data May 13, 1971 Japan 46-31575 [52] US. Cl 112/255, 242/147, 226/195 [51] Int. Cl D05b 47/00 [58] Field of Search.... 112/254, 255; 242/147, 149, 242/151; 19/237, 238; 226/195, 153

[56] References Cited UNITED STATES PATENTS 2,389,834 11/1945 Wyrick 226/153 X 2,866,427 12/1958 lrmscher 112/242 1,030,742 6/1912 Meyer 112/254 1,565,109 12/1925 Rose 226/153 x FOREIGN PATENTS OR APPLICATIONS 2,031,006 3/1971 Germany 242/150 M 1,014,017 12/1965 Great Britain 112/254 1,248,248 10/1960 France Primary ExaminerGeorge H. Krizmanich Attorney, Agent, or Firm-Cushman, Darby & Cushman [57] ABSTRACT According to the invention, the drawn-out thread of a sewing machine is guided between a roller having a thread releasing notch formed in part of the roller periphery and a thread urging member urged against the roller periphery, with the roller rotated in the direction opposite to the direction of withdrawal of the thread, so that the thread can be effectively rendered taut and loose alternately by the co-operation of the roller and thread urging member.

3 Claims, 5 Drawing Figures PATENIEDJAM 22 I974 SHEET 1 BF ilk! ICE/OR AET MEANS FOR IMPARTING TENSION TO THE DRAWN-OUT THREAD FOR SEWING MACHINES BACKGROUND OF THE INVENTION 1. Field of the Invention This invention generally relates to sewing machines and, more particularly, to means to impart tension to the progressively payed-out thread in a predetermined relation to the movement of the sewing machine nee die.

2. Description of the Prior Art Means to impart tension to the drawn-out thread for sewing machines are well known in the art.

A typical example of the tension imparting means is shown in FIG. I of the accompanying drawing. It comprises a drive shaft 2 rotatably provided in the machine body I and carrying an integral cam 3 co-operating with an actuating member 4 coupled through a coupling 5 to a rod 6 adapted to intermittently urge upper and lower dish-like thread clamping members 8 downwardly spring biased with a spring 7. With this construction, the drawn-out thread is intermittently clamped between the clamping members as the rod 6 tied through the coupling 5 to the actuating member 4 is vertically reciprocated by the rotation of the cam 3 with the drive shaft 2. In other words, the clamping members 8 are intermittently urged to each other, so that in some part of one machine operation cycle tension is imparted to the thread guided between the clamping members while in the other cycle the thread is released by the clamping members.

With the above construction, however, the actuating member cannot reliably follow the eccentric cam when the drive shaft is rotated at high speeds. Therefore, the clamping members sometimes fail to execute vertical excursion, resulting in a continued loose state of the thread, which results in sewing irregularity. Also, this imposes restriction upon the sewing speed. Further, intense noise is produced in the high-speed operation of the machine. Furthermore, this construction readily runs short of lubricating oil.

SUMMARY OF THE INVENTION The inventors have devoted extensive efforts to overcome the above drawbacks and succeeded in completing a tension imparting means which can obviate the above shortcomings.

An object of the invention is to provide a means to impart tension to the drawn-out thread for sewing machines, which is free from the failure of the vertical excursion of clamping members even at high speeds of drive shaft and is capable of exactly and reliably rendering the thread taut and loose to prevent the generation of the sewing irregularity.

A second object of the invention is to provide a means to impart tension to the drawn-out sewing thread for sewing machines, which can exactly and reliably render the thread taut and loose and enable realizing sewing operation at increased speeds.

A third object of the invention is to provide a means to impart tension to the drawn-out sewing thread for sewing machines, which is free from the generation of intense noise even in the high-speed operation of the machine, and in which the lubricating oil will not readilyget short.

A fourth object of the invention is to provide a means to impart tension to the drawn-out sewing thread for sewing machines, which is capable of exactly and reliably rendering the thread taut and loose and provides excellent response in the high-speed operation of the machine.

BRIEF DESCRIPTION OF THE DRAWING A iiEs c nii rioN 0E THE PREFERRED EMBODIMENT For the invention to be more fully understood, a preferred embodiment thereof will now be described by having reference to the accompanying drawing.

Referring to FIGS. 2 and 3, reference numeral 10 generally designates a tension imparting means embodying the invention. It has a roller ll secured to one end of a shaft 12 rotatably mounted in the machine body I. The roller 11 is formed with a planar notch or groove 13 cut in some part of the roller periphery. This groove 13 provides for the function of alternately rendering the thread clamped and released. That is, a drawn-out thread is rendered taut when a thread urging member designated by numeral 16 is urged against part of the roller periphery other than the part formed with the groove 13, and the drawn-out thread is rendered loose when the thread urging member 16 is urged against the roller periphery part formed with the groove 13 so that the thread is drawn out at higher speeds than the time when it is taut. This alternative taut and loose action of the thread is achieved by the rotation of the roller 1 I, thus feeding the thread successively. Secured to the other end of the shaft 12 is a bevel gear 14 meshing with another bevel gear 15 secured to a drive shaft 2 rotatably mounted in the machine body I. The drive shaft 2 also drives a thread draw-out means not shown. The roller 11 is adapted to complete one rotation with one rotation of the drive shaft 2.

The thread urging member has a hooklike form with its arcuate portion 17 urged against the periphery of the roller 11. The thread urging member I6 is pivoted to the machine body 1 by a pin 18 mounted on the machine body.

The opposite end of the thread urging member 16 is freely movably fitted on an angleshaped guide rod 19 mounted on the machine body 1 with a vertical portion 23 embedded in the machine body 1. And on the threaded end of the guide rod 19 there is fitted a nut 21 and a coil spring 22 is intervened between the nut 21 and said opposite end of the thread urging member 16. Thus, the arcular portion 17 of the thread urging member 16 is movably urged against the periphery of the roller 11 with respect to the pin 18 in such a manner that said opposite end of the thread urging member 16 is urged by the coil spring 22, as shown in FIG. 2.

Numeral 24 in FIG. 2 designates the thread being drawn out. The roller 11 is rotated in the direction opposite to the direction of progress of the thread 24. The groove 13 formed in the periphery of the roller 13 is slightly narrower than the width of the urging area of the urging member 16.

In the operation of the tension imparting means of the above construction, the torque of the drive shaft 2 rotated in synchronism with the machine operation is transmitted through the bevel gears 15 and 14 to the shaft 12 to rotate the same. With the rotation of the shaft 12 the roller 11 integral therewith also rotates, while the arcular portion 17 of the urging member 16 is held urged against the revolving roller periphery of the roller 11 by the coil spring 22. The thread 24 is guided in the direction of solid arrow in FIG. 2 between the roller 11 and the arcular portion 17 of the urging member 16. When the arcuate portion 17 is engaging with part of the roller periphery other than the part formed with the groove l3 during part of the machine cycle, as shown in FIG. 4, the drawn-out thread 24 is rendered taut. On the other hand, when the arcuate portion 17 is engaging with the roller periphery part formed with the groove 13, as shown in FIG. 5, the drawn-out thread 24 is rendered loose. in the above manner, the thread is alternately rendered taut and loose in accordance with the machine cycle.

As has been described in the foregoing, with the arrangement according to the invention wherein the drawn-out thread is guided between the periphery of a roller formed with a thread relaxation notch or groove and rotated in the direction opposite to the direction of progress of the thread and a thread urging member urged against the roller periphery, when the urging member is in frictional contact with part of the roller periphery other than the part formed with the thread relaxation groove the thread is frictionally clamped between the roller and the urging member to experience tension, whereas when the urging area of the urging member coincides with the thread relaxiation groove the thread is released from the clamping and is ready to be freely drawn out. In the above manner, the alternate rendering of the thread taut and loose is achieved through the roller and the urging member urged against the roller periphery, so that the response of the tension imparting means particularly in the high speed operation of the machine is excellent and the feed of the thread drawn out can be exactly and reliably timed to the movement of the sewing machine needle. Thus, sewing irregularity which might occur with the conventional sewing machines can be eliminated. Also, noise can be eliminated even in the high-speed operation of the sewing machine.

What is claimed is:

1. ln a sewing machine, a sewing machine body and means for imparting tension to a thread being fed comprising:

a roller;

means journalling the roller on said body and rotating the roller opposite to the direction of feeding of the thread being fed;

means defining a generally tangentially proceeding notch in the radially outer periphery of the roller, said notch being of less than circumferential extent, the radial extent of the roller thus being greater angularly beyond the notch than within the notch;

a generally L-shaped thread urging member having means defining a convex arcuate surface on one leg thereof;

pin means pivotally mounting the thread urging member on the body; and

means resiliently biasing the thread urging member about the pin means in a sense to bias the convex arcuate surface of the thread urging member into resilient contact with the radially outer periphery of the roller;

the shape and extent of the convex arcuate surface relative to the shape and extent of the radially outer periphery of the roller being such that the convex arcuate surface fails to full obstruct the notch and defines a gap that is open from one angular extreme of the notch to the other when the notch is presented toward the convex arcuate surface, said gap being sufficient in thickness to permit the thread being fed between the roller and the convex arcuate surface to slip forwards when the notch is presented toward the convex arcuate surface.

2. The apparatus of claim 1 wherein the resilient biasing means comprises:

means defining an opening through the other leg of said thread urging member;

an L-shaped rod having one leg mounted on the body and having the other leg loosely extending through said opening; threading on said other leg of the rod outwardly beyond said opening;

nut means threaded on said threading; and a compression coil spring about said other leg of the rod urging between the not means and the other leg of the rod.

3. The apparatus of claim 1 wherein the notch is shorter, axially of the roller, than said convex arcuate surface to prevent that surface from entering the notch. k 

1. In a sewing machine, a sewing machine body and means for imparting tension to a thread being fed comprising: a roller; means journalling the roller on said body and rotating the roller opposite to the direction of feeding of the thread being fed; means defining a generally tangentially proceeding notch in the radially outer periphery of the roller, said notch being of less than circumferential extent, the radial extent of the roller thus being greater angularly beyond the notch than within the notch; a generally L-shaped thread urging member having means defining a convex arcuate surface on one leg thereof; pin means pivotally mounting the thread urging member on the body; and means resiliently biasing the thread urging member about the pin means in a sense to bias the convex arcuate surface of the thread urging member into resilient contact with the radially outer periphery of the roller; the shape and extent of the convex arcuate surface relative to the shape and extent of the radially outer periphery of the roller being such that the convex arcuate surface fails to full obstruct the notch and defines a gap that is open from one angular extreme of the notch to the other when the notch is presented toward the convex arcuate surface, said gap being sufficient in thickness to permit the thread being fed between the roller and the convex arcuate surface to slip forwards when the notch is presented toward the convex arcuate surface.
 2. The apparatus of claim 1 wherein the resilient biasing means comprises: means defining an opening through the other leg of said thread urging member; an L-shaped rod having one leg mounted on the body and having the other leg loosely extending through said opening; threading on said other leg of the rod outwardly beyond said opening; nut means threaded on said threading; and a compression coil spring about said other leg of the rod urging betweEn the not means and the other leg of the rod.
 3. The apparatus of claim 1 wherein the notch is shorter, axially of the roller, than said convex arcuate surface to prevent that surface from entering the notch. 